This is it! Foursquare has once again created a special badge and logo for 4sqday! We’re super proud to unveil the new 4sqday 2011 logo and confirm that users will be able to unlock a 4sqday badge by checking in on April 16th, 2011! Details on exactly how to unlock the badge has yet to be revealed, but stay tuned! via Announcing the official foursquare badge, logo and T-shirt! « Foursquare Day.
There are several sites aligning themselves with this day/event, but nothing from foursquare officially. That makes me think this it is a grass-root movement. It’s cool though.
According to their tweet today it appears McDonalds is planning something for 4/16/11.